Field of the Invention
The disclosure generally relates to the oil field equipment. Specifically, the disclosure relates to the test equipment for blowout preventers.
Description of the Related Art
With the tragic incident of an offshore explosion caused when a safety blowout preventer (“BOP”) failed to close a subsea oil well after a gas leak, more engineering designing and testing of blowout preventers are being done by those in the oil field industry. A fatigue test simulates well tubing being inserted through the BOP to determine whether the BOP can hold pressure over its expected life. A known BOP test system is shown in FIG. 1. The BOP test system 102 includes a reservoir 104 of hydraulic fluid with supply lines 116 connected to pumps 106. The pumps 106 supply pressurized hydraulic fluid to a high pressure filter 120 through supply lines 118 and then to a hydraulic control valve 108. The control valve 108 controls hydraulic fluid flow into and out of a hydraulic cylinder 110. A heat exchanger 122 cools the hydraulic fluid in the reservoir. The hydraulic cylinder 110 repetitiously raises and lowers a hollow mandrel through internal BOP seals (not shown) to test the BOP design and integrity. The large number of quick repetitions conducted for the test causes friction that causes heat on the seals, which is not experienced in the field. To better simulate field conditions, the seals are cooled by a fluid. A cooling system with a coolant reservoir, pump, and heat exchanger is attached to a lower portion of the BOP test system. Coolant enters through a flanged base that is attached to a chamber below the BOP and flows upward through a cooling tube that is smaller in diameter than the mandrel inside diameter. As the mandrel raises and lowers through the BOP seals, the fixed position inner tube sprays or otherwise flows the coolant on the inside of the mandrel. However, the inner tube only flows the coolant to the particular surface of the mandrel that is adjacent the inner tube at a particular time during that portion of the mandrel stroke as the mandrel is raised and lowered. The inner tube is not able to flow fresh coolant to any mandrel inside surface that is above the inner tube for other portions of the stroke. Proportionately, at least one-half of the mandrel is therefore not cooled with flowing coolant during a given full stroke of the mandrel.
There remains then a need to provide a better cooling system for the mandrel during a greater portion the mandrel stroke.